CENTAUR BINARIES

On January 20, 2006, the Hubble Space Telescope was aimed at the Centaur #42355 (2002 CR46), and were stunned to find out that it was actually a binary. That is, a two-body system, with one part orbiting the other at a distance of 1,300 kilometers (800 miles). (CR46 was originally discovered February 5, 2002, so it took astronomers almost four years to discover it had a moon.)

While other binary minor planets have been found, CR46 was the first known binary Centaur. This led astronomers into all sorts of speculations, including the possibility that there may be binary comets orbiting our Sun.

It's eccentricity is 0.5407609, and an orbital period of 235.76 years. (Typhon and Echidna's orbital elements.) First thing I thought when I read that was that the orbit was huge compared to the other Centaurs. We'll go back to that in a moment.

Only a few months later, on April 11, 2006, a second binary Centaur was observed, #65489 (2003 FX128). (FX128 had been originally discovered March 22, 2003.)(

But this body had an even stranger orbit for a Centaur than CR46. The eccentricity was 0.8258985, and the orbital period of 1,039.67 years! (Ceto and Phorcys' orbital elements.) When astronomers realized this, they did some thinking, and reclassified both of these bodies. They are now no longer called Centaurs. Rather, they are SDO's, or Scattered Disk Objects. (I'm actually relieved, considering the names they later were given!)

#42355 was named Typhon on November 9, 2006. Typhon was god of wind, whose parents were Gaia and Tartarus. Typhon was oft descried as the largest, most grotesque of all creatures, often pictured as having a hundred serpent heads. He attempted to overthrow Zeus and take over, but Zeus defeated him by crushing Mount Etna on him.

Typhon's companion, or moon, was named Echidna. Hesiod wrote that Echidna was
Typhon's mate, and together they gave birth to almost every horrible monster in Greek mythology.

#65489 was named Ceto on the same date, November 9, 2006, after a terrible sea monster, daughter of Gaia and Pontus, who personified all the known an unknown dangers and terrible creatures in the sea. Ceto, in fact, became short for sea monster, and the word Cetacean was derived from her name.

Ceto's moon was named Phorcys, after her husband in mythology, they also gave birth to many terrible children, including the Gorgons such as Medusa.

Now do you see why I'm glad they weren't kept as Centaurs?

For those interested, here is a 2008-2012 ephemeris, for every fifteen days, for Typhon and Ceto. It is set to 0 Hr UT: